Monday, May 21, 2012
   
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Sound

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Subject Index - Science


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1.  Sound is energy that is made by vibrations. When any object vibrates it causes movement in the air.
The air particles then bumps into each other and then bump into others. This continued bumping cause
a sound wave.

2.  If the human ear is within the range of the vibrations, a sound can be heard.

3.  When the vibrations are fast, the sound is high. When the vibrations are slow, the sound is low.

4.  Sound waves are also called pressure waves because they move the particles they are passing through.

5.  The ear is not the only detector people and animals have. Sound waves can even be felt by different
parts of the body. Sometimes you can feel the vibrations thunder makes while you are actually hearing it.

6.  Stringed instruments are played when fingers or a bar are pressed down on the strings. This pressure
changes the strings' length, causing them to vibrate at different frequencies and make different sounds.
Shortening a string makes it sound higher, while lengthening a string can produce a lower sound.
Strings also produce different sounds depending on how thick they are.

7.  In wind instruments, there is a reed (a thin piece of wood inside the mouthpiece, that vibrates
when air travels over it. The keys produce different size openings in the instrument.  The air columns
inside the instrument are then made shorter or longer which produces different sounds.

8.  Sound waves can bend around corners and obstacles.

9.  The human ear that is attached to the side of the head acts as a funnel to catch sounds. The inner ears,
eardrums and tiny bones inside the ear called the hammer, anvil and stirrup all begin to vibrate. Sound
vibrations then move through an oval opening called the cochlea. In the cochlea--a snail shell-like,
fluid-filled chamber--the sound waves stimulate tiny hairs that are connected to the auditory nerve.
The auditory nerve receives signals from the nerve cells and transmits them to the auditory center in the brain.

10.  The brain receives these messages from the auditory nerve. The messages comes in fast and furious,
in a jumble of confusion, but the brain has the ability to sort them into an organized pattern.
This way we can understand the sounds we hear as music or human speech.
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